Virginia Research Day 2021

Proposed Injury Threshold for Drone Blade Lacerations Lauren A. Duma, Mark T. Begonia, Barry Miller, Stefan M. Duma

Introduction

As the use of drones becomes increasingly popular and more widespread, the number of drone related injuries has the potential to increase. Drone accidents have caused a variety of injuries, including head injuries with loss of consciousness, open globe eye lacerations, and skin lacerations [1-4] (Figure 1). The objective of this study was to determine the different properties of various drone propellers that cause laceration injuries and to propose an injury threshold that can be used to reduce the risk of skin lacerations.

Figure 4: The fetal bovine skin surrogate, showing a minor laceration, after making contact with the Air Car A380 in test 9.

Figure 1: Skin lacerations caused by the Mavic drone [6].

Figure 3: Side view of the testing setup for the bovine skin impact tests. The surrogate was moved into contact with the Phantom 4 .

Results and Discussion

80 ft/s

200 ft/s

Minor abrasions were only observed at blade tip speeds higher than 80 ft/s, and minor lacerations were only observed at blade tip speeds higher than 200 ft/s (Table 1). For example, the Air Car A380 caused a minor laceration when the drone blades at 313.1 ft/s came into contact with the fetal bovine skin (Figure 4). Overall, injury severity had the strongest correlation to tip speed (r2=0.79). However, injury severity did not correlate as strongly to angular velocity (r2=0.56), blade length (r2=0.03), and blade tip thickness (r2<0.01) (Figure 5).

Materials and Methods

A total of seventeen experiments were performed using nine different toy drones. For each drone, the blade tip thickness, blade length, and angular velocity (rpm) were recorded. A laser tachometer was used to measure the angular velocity. Blade tip velocity was calculated using the angular velocity and blade length. Each experiment had full contact with the blade at speed into the skin surrogate, second trimester fetal bovine skin (Figures 2 and 3). This skin surrogate was used due to its ability to accurately model drone blade laceration injuries in human skin [5]. The observed injury caused by the drone was then assigned a level of injury severity: 0 for no injury, 1 for a minor abrasion, and 2 for a minor laceration.

Table 1 : Test configuration and results for each experiment .

Test

Drone

Observed Injury

Blade tip thickness (in)

Blade length (in)

Angular Velocity (rpm)

Blade tip Speed (ft/s)

[1] Moskowitz, E.E. et al, Am J of Ophthalmology, 10, 35-37, 2018. [2] Ranamukhaarachchi, S.A. et al., Nature , 6:32074, 2016. [3] Reed, Matthew P. et al., SAE , paper number 942217, 1994. [4] Papy, Alexandra et al., IRCOBI , 2012. [5] Duma, Lauren A. et al., BMES, 2019. [6] https://mavicpilots.com/threads/any-reason-not-to-hand- catch.69583/page-2 Conclusions 1) Blade tip speed proved to contribute the most to laceration injuries caused by drone blades, with speeds above 80 ft/s causing minor abrasions and speeds above 200 ft/s causing minor lacerations. 2) In order to avoid severe injuries caused by drone propellers, maximum blade tip speed should stay below the threshold of 200 ft/s, especially for drones designed for toy use. 3) All other parameters (blade tip thickness, blade length, and blade angular velocity) were not correlated to risk of skin injury . Figure 5 : Injury severity vs tip speed for all tests . References

1 2 3 4 5 6 7 8 9

Phantom 4 Advanced 0.035

4.70 8115 332.8 Laceration

Air Hogs Axis 200

0.020

2.52 2181 48.0 3.77 1526 50.2 3.08 3330 89.4 2.38 4605 95.6

No injury No injury

Air Hogs Battle Tracker 0.016

Air Hogs 4T2010 Star Wars X-Wing Fighter Gyroscopes System

0.016 0.018

Minor abrasion Minor abrasion

0.021

3.82 2569 85.6

Minor abrasion

Syma FPV Real-Time 0.027 Holy Stone HS-Series 0.021

2.63 5730 131.5 Minor abrasion 2.86 6072 151.5 Minor abrasion 1.08 33226 313.1 Minor laceration

Air Car A380

0.015

10 Air Car A380

0.015 0.015

1.08 11030 104.0 Minor abrasion 1.08 24960 235.2 Minor laceration

11

Air Car A380

12 Air Car A380

0.015

1.08 30493 287.4 Minor laceration

13 Air Car A380 14 Air Car A380

0.015 0.015

1.08 7099 66.9 1.08 8658 81.6 2.86 2971 74.2

No injury

Minor abrasion

15 Holy Stone HS-Series 0.021 16 Holy Stone HS-Series 0.021 17 Syma FPV Real-Time 0.027

No injury

Figure 2: Aerial view of the skin laceration tests. The skin surrogate was moved into contact with the Phantom 4.

2.86 6125 152.9 Minor abrasion

2.63 2719 62.4

No injury

Presented at VCOM Research Day 2021

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